DE102005013252A1 - Ablation program establishing method for correcting ametropia of human eye, involves establishing ablation program based on water concentration of surface to be ablated and pre-compensated set-point ablation profile - Google Patents

Abstract

The method involves discharging pulses of a pulsed laser beam onto a surface e.g. cornea, to be ablated based on a predefined set-point ablation profile. A pre-compensated set-point ablation profile is determined based on the shape of the laser beam profile and the inclination of the surface to be ablated. Ablation program is established based on the pre-compensated profile and the water concentration of the surface to be ablated. Independent claims are also included for the following: (1) a device for establishing an ablation program (2) a computer program product including program code, which when executed establishes an ablation program.

Description

The The present invention relates to a method of construction an ablation program for the Ablation of hydrous material from a surface of a body according to one predetermined target ablation profile by the delivery of pulses of a pulsed laser beam on the surface, a method of formation control signals for controlling a laser ablation device for ablating water containing material from a surface of a body according to one predetermined target ablation profile by means of pulses of one of the laser ablation device emitted pulsed laser beam, and means for performing this Method.

The Ablation, that is the removal of material from a surface of a body by means of a pulsed Laser beam is basically known. The ablation becomes laser radiation or a laser beam on the surface to be ablated directed, on the material of the body absorbed at least a portion of the laser radiation and at sufficient intensity or sufficient energy input is removed from the surface. The laser ablation can therefore be used to contact a body without contact with high accuracy, especially at low ablation depths, to shape.

to Shaping various methods of laser ablation are known. In a variant that is responsible for the removal of one in the ablation area approximately spherical body is suitable, laser beam pulses are directed to the surface, wherein according to a predetermined ablation program of the destination to which the respective Pulse is to be steered, and the shape and size of the beam cross section the surface, be set. Often is the destination for all pulses are constant and will not be specified explicitly.

at another particularly important variant, also referred to as a "spot-scanning" method, becomes material from the surface ablated by a pulsed laser beam according to a predetermined ablation program on the surface guided becomes. Below the ablation program is a sequence of destinations on the surface or by corresponding data representing the locations of the destinations, be directed to the respective at least one pulse of the laser beam should. Are the beam or pulse properties of the laser radiation used variable, the ablation program may further contain at least one indication the one ray or pulse property, in particular the energy of the pulse or the fluence, that is to say the energy of the pulse on the irradiated area detected on an orthogonal to the direction of the laser beam on the surface of the body arranged level, indicating. Does the laser work during an ablation? constant pulse energy or fluence, need data that the pulse energy or Fluence, not for each pulse or destination to be specified.

The Ablation program is based on a predetermined target ablation profile determined, i. the indication of desired Ablation depths or depths of the ablation of the material to be ablated by the pulses in dependence from the place on the surface. To create the ablation program, it is often assumed that everyone Pulse a single pulse ablation volume ablates, that through the cross section of the laser beam at the for this Purpose as orthogonal to the beam direction assumed surface and given by the ablation depth. Meet several pulses at the same Place on, add up the ablation depths, so that in total a greater depth is achieved. The ablation program is now determined by Delivering the pulses corresponding single pulse ablation volumes to the ablated by the ablation program specified destinations from the surface so be that total preferably good the desired Target ablation profile is achieved.

Around by ablation the desired Ablation profile, that is the desired ablation profile, as accurately as possible It is essential that when creating the ablation program the erosive effect of a single pulse is well known.

One important application of laser ablation according to the so-called "spot-scanning" method is the laser ablation of Plastic lenses, such as contact lenses, or in particular also of corneal tissue in photorefractive keratectomy (PRK) or LASIK for the correction of defective vision, in particular of the human Eye.

In the treatment of the refractive error of the human eye by ablation with an excimer laser, the cornea or cornea of the eye is shaped by ablation in such a way that a refractive error which causes defective vision is eliminated as far as possible. With conventional methods, the ge desired refraction in about 95% of cases to be exactly reached to about +/- 1 diopter.

In individual cases can however, night vision problems and a reduction of contrast sensitivity in twilight vision occur on changes in the asphericity of the cornea due to the laser surgical treatment. The cornea is at a healthy or non-refractive eye rather stretched and has a negative asphericity with values of the asparticity parameter Q of about -0.25. This asphericity compensates spherical Aberrations of the lens of the eye. After a laser surgery Treatment of myopia, the cornea tends to be flattened, the asphericity being essential is larger as in the healthy or non-refractive eye. These deviations can be at least partially due to that achieved by the ablation Actual ablation profile deviates from the predetermined target ablation profile.

to Improvement of the ablation are in WO 95/27534 a method and a system for performing photorefractive Keratectomy to produce a desired refractive correction of the corneal tissue. Use the procedure and the system a control of the action of liquid on the surface of the Cornea, to the disturbing Influence of liquid to the desired Ablation process under simultaneous To maintain the water content of the cornea. It will proposed the mean repetition rate of delivered to the corneal surface To control pulses, an accumulation of fluid between the pulses reduce without dehydrating the cornea, or increased fluence of the on the cornea surface to choose the delivered pulse to reduce the effect of accumulation of fluid on the corneal surface. It is also proposed that before delivering a pulse for ablation to a location fed to this evaporation energy becomes.

The However, known methods still leave room for improving the accuracy ablation by using an improved ablation program.

Of the The present invention is therefore based on the object, a method for the preparation of an ablation program for the ablation of hydrous Material from a surface of a body according to one predetermined target ablation profile by the delivery of pulses of a pulsed laser beam to the surface, to create that through the characteristics of the body conditional deviations between the desired ablation profile and the indeed actual ablation profile achieved during ablation using the ablation program keeps low. Another object of the invention is to provide Means of implementation of the method.

The Task is solved by a method of creating an ablation program for the ablation of aqueous material from a surface of a body according to a predetermined target ablation profile by the delivery of pulses of a pulsed laser beam to the Surface, where the ablation program is based on the desired ablation profile considering a water content of the ablatierenden material is created.

Under an ablation program, in particular the ablation program according to the invention becomes an ablation program to be used for ablation, as described above, at least one statement of a sequence of Beam shaping of a pulsed laser beam and / or target locations or -directions understood with those or on the or in the pulses of the laser beam are emitted. Additionally, the ablation program either for the entire sequence a value of the pulse energy or fluence or for each Pulse or groups of pulses each have a value of that for the pulse or the pulse group to be used pulse energy or Fluence or pretend. In the second case, the values may vary depending on the destination be. Below the ablation profile is an indication of the depth depending on the ablation from the place on the surface or understood from a direction of the laser beam with respect to the body. So it can be a desired, theoretical or actual Act profile.

The procedure for creating an ablation program is based on a predetermined target ablation profile. The desired ablation profile can be specified in any manner. For example, points on a given dot matrix in a reference plane and the points respectively assigned ablation depth data may be given. However, it is also possible to specify the desired ablation profile by at least one function parameterized by at least one function parameter and a value of the function parameter, wherein the function and the value of the function parameter are chosen such that the function depends on the value of the function parameter and on location in the reference plane the Ab indicates the depth of When represented by functions, polynomials, splines, Zernike polynomials or other representations may be used, for example.

The Method is to create an ablation program for ablation provided by hydrous material. The water can be in of any concentration or with any weight or weight Volume fraction may be contained in the material, wherein the material however, at least substantially on a time scale of minutes dimensionally stable. The water can be in a matrix embedded or, preferably physically, to another substance be bound to the material. In particular, it may be in the material to act on biological tissue. Particular preference may be given to the process for the Ablation of material used by the cornea of the human eye become. For consideration the water content of this can in particular in the form of appropriate Be given data. The water can, of course, other substances include, for example, salts or other solutes.

The Invention is based inter alia on the idea that with Delivery of a laser pulse to the body caused ablation depth, up to which material is ablated with the single laser pulse, depends on the water content in the volume to be ablated. These dependence could For example, be conditional that the ablation energy a pulse for detachment of the entire material including the material contained therein Water serves. The water may have a different absorption for the laser radiation and another heat of vaporization have as at least one other substance, which comprises the material. Changes the water content, can due to the changed Composition of the material also change its ablation properties.

Of the Water content will now be used when creating the ablation program preferably considered in such a way that this In the case of an ablation according to the ablation program, the actual ablation profile achieved as well as possible corresponds to the desired ablation profile. The goal is first and foremost the consideration of the water content as a guideline for the specification of the characteristics and destinations to be delivered pulses, not but influencing the water content for example in the sense that this is kept constant. So it is not tried by choice the ablation conditions the water content of the body, such as the cornea or a liquid film on the body preferably constant, but the ablation program will be found or the expected water content of the body.

The consideration the water content can be carried out in particular in the form that the dependency the ablating effect of a pulse on the water content, in particular a variation of the water content, and optionally in addition the change the water content is detected by the ablation. Variations of the water content can especially for a body locally and during the course of the ablation, temporally, and then between several bodies as Deviation from a typical, for example statistical, mean occur.

The consideration the water content allows the creation of an ablation program, which results in ablation to an actual ablation profile that the target ablation profile also in varying from ablation to ablation water levels or comes very close to varying in the material water contents or matches this. This is particularly advantageous when ablating on biological tissue.

The Ablation program may still depend on other variables, such as beam parameters like the beam diameter at the surface of the body, the pulse energy used or Fluence, the pulse repetition rate, as well as other material properties of the material to be ablated.

The inventive preparation method can by means of a creation device according to the invention carried out become. Such a device for creating an ablation program for the Ablation of hydrous material from a surface of a body according to one predetermined target ablation profile by the delivery of pulses over the surface guided pulsed laser beam to the surface comprises a data processing device, to carry out the method according to the invention is designed to create an ablation program.

In particular, the data processing device can have a processor for processing a computer program, by means of which the ablation program can be created in accordance with the inventive construction method when the computer program is executed on the computer, and a memory in which the program is stored. In addition, the data processing device may still have a physical and / or software interface via which the desired ablation profile or data for its calculation into the device can be read in or entered. This is especially from before if a different target ablation profile is to be used for different ablations.

Another The invention relates to a method for forming control signals for controlling a laser of a laser ablation device for delivery a pulsed laser beam and / or a deflection of the Laser ablation device for deflecting the laser beam to hydrous Material from a surface of a body according to one predetermined target ablation profile by means of pulses of a pulsed Ablate laser beam, in which with the inventive production method an ablation program for the predetermined target ablation profile is created and accordingly the ablation program control signals to the laser and / or the deflector be delivered.

Accordingly the invention is also a device for the formation of Control signals for a laser and / or a deflection device of a laser ablation device, aqueous material from a surface of a body according to a predetermined target ablation profile ablate by pulses of a pulsed laser beam, wherein the device an inventive device for creating creation an ablation program from the given target ablation profile and a control device for outputting control signals in accordance with the created Ablation program to the laser and / or the deflector for Deflection of the laser beam emitted by the laser comprises.

The Control device, by means of which the control signals are formed and can preferably be issued, it can be independent of the data processing device trained and with this by a data connection for transmission be connected to the ablation program. Preferably, it is at least partly by means of the data processing device realized by means of which through the ablation program in conjunction with corresponding circuits of the control device control commands can be delivered to the laser and / or the deflector, whereby advantageously results in a particularly simple structure. The deflector and the laser are dependent from the ablation program created by the authoring device controlled by the control signals formed so that pulses of the pulsed laser beam emitted by the laser beam to corresponding Destinations on the surface be steered.

The Laser ablation apparatus may in particular the control signal forming device include, which gives the advantage of a particularly compact design results. Preferably, therefore, in the laser ablation device the laser and / or the deflection device with the control device via a corresponding control connection connected.

A Ablation according to the above-mentioned "spot scanning" method has the advantage that easy Extensive ablation profiles can be ablated. The Creation method and the creation device therefore serve preferably for creating an ablation program for the ablation of hydrous material from a surface of a body in accordance with a predetermined target ablation profile the delivery of pulses one over the surface out pulsed laser beam on the surface. The ablation program comprises then preferably a series of destinations or directions, with to which or on the or in the pulses of the laser beam become. If successive pulses are delivered to the same destination, the destination only needs to be given once, if at the same time the number of pulses to be delivered to the destination is indicated.

in principle it may be sufficient in the creation process, the water content of the material as constant for to assume the entire volume to be ablated. However, it is preferable that at the creation of the ablation program the water content depending from the place on the surface or in an area to be ablated. This procedure has the advantage that for a local difference in water content in the area to be ablated, which is defined by the desired ablation profile, or volume and on the other by the ablation caused differences, for example between the edges of the ablating region and its center can be what a higher one Precision of Ablation leads.

The water content may preferably be taken into account in preparing the ablation program to be used for ablation, by using a model that determines the dependence of the ablation depth achieved by at least one pulse delivered to a target site on the surface or at least one target location Surface emitted pulse reproduced ablation volume of the water content of the pulse to be ablated with the material reproduces. The model can be given in particular by a function that depends on a dependent on the water content or reproducing size and the Ablationstiefe for a pulse of the pulsed laser beam with vorge Been pulse characteristics, eg given pulse energy or Fluence, at least approximately reproduces. Such models can be obtained from theoretical considerations or from experimental studies of ablation depth or ablation volume in single-pulse ablation as a function of at least the water content, and subsequent presentation of the results by suitable functions. In particular, the model can be considered in a method step or in a computer program, by means of which the creation method is carried out, in such a way that formulas derived from the model are evaluated with parameters of the model during program execution.

Preferably contains the model as a parameter an ablation rate that depends on the water content dependent is. This can be taken into account in an advantageous manner that the water content influences the ablation depth.

typically, does not lead every laser pulse to an ablation. Preferably, therefore, in the Method a Fluence threshold for the ablation of material from the surface of the body used and the threshold value depending on the water content determined. This approach has the advantage of being simple and controlled Make an effect of the water contained in the material on it, if any Ablation occurs can be.

information to the water content in the material can vary on different kind and flow into the process. It basically only need appropriate data to be used. So can a fixed another model for the water content for a predetermined type of material may be used, including the data processing device the creation device a corresponding in a memory Having in the creation device stored program module can, in which the further model including appropriate parameter values is hard coded. Alternatively, a parameter value may also be in a parameter file be stored firmly.

Already on one area of the body delivered pulses can already an influence on have the water content of the area or adjacent areas. It is therefore preferred that at the creation process, a further model is used for one given area of the material influence of this area or adjacent areas of impinged pulses of the pulsed laser beam on the water content. The model needs the influence only approximately play. In particular, the model can influence it to reproduce that depends on the target ablation depth in the range that approximates the Number of pulses to be delivered to the area, possibly in nonlinear way, corresponds. Under range can be in particular a substantially orthogonal to the surface extending column of Material to be understood, which successively by impinging pulses is ablated, wherein the water content in the remaining Part of the column changed by the ablation. This procedure has the advantage that during the ablation a measurement the water content is not absolutely necessary. The ablation program considered the effect already at its creation. Preferably that is Model for the ablation depth or the ablation volume and the other model chosen so that with increasing target ablation depth or increasing number on the same Range of pulses to be delivered, the ablation effect of a pulse increases, i.e. the ablation depth generated by a pulse or by the ablation volume produced by the pulse increases. This allows in particular the problems with the correction of short or farsightedness with conventional ablation methods are reduced in which Areas of low target ablation depth actually achieved ablation too low compared to the target ablation depth fails.

However, if variations in the water content of the otherwise substantially similar material may occur to different bodies and / or to be able to create ablation programs for the ablation of various materials, preferably data is collected in the method of preparation which determines the water content, particularly on the surface or spatially resolved in the area to be ablated, or from which the water content, in particular on the surface or in the area to be ablated, can be determined in a spatially resolved manner. It is then preferred that the generating device comprise an interface for acquiring data representing the water content of the material or from which the water content can be determined. Preferably, the data processing device is designed to determine the water content from the data from which the water content of the material can be determined. If the water content is assumed to be constant in the area to be ablated, it may be sufficient to read only a corresponding value via the interface. If the water content is considered spatially resolved, corresponding data in the form of a field can be given of values of a parameter representing water content at predetermined interpolation points in the volume to be ablated or on a reference surface for describing the volume. Alternatively, it is possible to adjust the water content through a parameterized, local dependent function by specifying the values of the parameters of the function.

The Information about the water content can be determined in different ways. That's how it is an embodiment preferred that the Water content from empirical investigations of different samples of the material is determined. In particular, in the case of biological Material screening of material or fabric of the same Type, but are performed by different individuals of a species, in which a mean water content is determined, which then in the creation of the ablation program is incorporated. In particular, in this Be assumed that the Water content in the entire area to be treated approximately is constant. This procedure has the advantage that there is no individual data about each body to be treated and therefore easy and quick to apply. Especially can corresponding values are stored permanently in the data processing device but also an input via an aforementioned interface possible is.

in the Over the course of the ablation, the water content of the material may submerge circumstances change through the ablation. It is therefore preferred in the method of construction that for consideration the water content during the creation of the ablation program Model for the water content or the change the water content of the material as a function of at least the Number and / or location previously on the same place and / or adjacent Places emitted pulses is used. In an advantageous way such a consideration the change the water content by ablation done without a measurement the water content during ablation is necessary. Values possibly occurring in the model Parameters can as previously determined empirically, for example.

Around high accuracy of ablation, i. a slight deviation between desired ablation profile and by the ablation according to the created and actual ablation profile achieved using the ablation program however, it is preferred that in the process of preparation the water content on the body measured data is determined. This has the advantage that no Assumptions about need to be used the water content. The water content need not be calculated explicitly, but it can sufficient that one determined this uniquely determining size which is then inserted into a formula in which the dependency replaced by the water content itself by the dependence on the size is. The data processing device of the creation device is preferably designed to measure the water content of the body To determine data. For this purpose, a in the data processing device running computer program corresponding program code. The measurement of the data can be done before the ablation program is created and in particular ablation or during the creation of the ablation program and the formation of the control signals.

The Data can in particular, for example via a suitable one mentioned above Interface, from a disk, a user interface or a measuring device are read. Preferably, the data is automatically measured on the body, for which the creation device a control interface for a measuring device for measuring data on the body, which reflect the water content or from which the water content can be determined, via the control commands for detection of measured data to the measuring device can be dispensed. In this way, the total processing time be significantly reduced.

Preferably be as on the body Measured data uses data that is a spatially resolved determination the water content in the material at the surface or in a to be ablated Enable area. If the data is measured automatically, the measurement is done accordingly preferably spatially resolved in the material on the surface or in an area to be ablated. This way, in Advantageously, the water content are considered location-dependent, resulting in a increased Accuracy of ablation leads.

The Data can be detected before the actual ablation. At a special preferred embodiment However, according to the invention, corresponding data will also be obtained during the Formation of control signals according to a first part of the ablation program or during ablation, so that a very accurate control of ablation possible is.

The water content can be determined in different ways. In particular, one of the possibilities mentioned below or a combination of these possibilities can be used. In a first alternative of the construction method, data are used to determine the water content, which reflect the temperature of the surface. For this purpose, the creation device may preferably have a device for detecting a temperature of the surface, which detected for the transmission of Temperature data is connected to the data processing device via a data link to the data processing device, and wherein the data processing device is designed to determine the water content of the material in dependence on the temperature data. This embodiment has the advantage that a temperature measurement can also be carried out in a contact-free, spatially resolved manner if, for example, corresponding infrared cameras are used as the measuring device.

When another possibility it is preferred that Determining the water content data are used properties from optical radiation emitted by the material in the ablating area of the body emanates. Preferably, the corresponding data automatically detected. The creation device may for this purpose preferably one with the Data processing device via a data link connected spectrometer for the analysis of the radiation of the body to be ablated exhibit. The data processing device can then be used to determine the water content in dependence from the spectrometer detected Data be formed. For this purpose, a in the data processing device stored computer program Program code for determining the water content dependent on from the spectrometer detected Data included. This alternative has the advantage that on the one hand a non-contact Data collection possible and on the other hand an accurate recording of the water content is possible. About that It is also possible the radiation is spatially resolved to record and thus a location-dependent determination of the water content to enable. In a laser ablation device with a laser for delivering the Laser beam and a creation device is the gaze or Detection direction of the spectrometer preferably over the Laser beam on the surface of the body inclined. this makes possible a simple integration of the spectrometer in the laser ablation device.

Especially Preferably, data are used to determine the water content, by confocal Raman spectroscopy of optical radiation from the surface available are. The creation device preferably has a device for this purpose to carry out of confocal Raman spectroscopy for the transmission of acquired spectroscopy data to the data processing device via a data connection with the data processing device is connected, wherein the data processing device preferably for determining the water content of the material in dependence is formed by the spectroscopy data. This procedure allows a very good specificity the measurement for Water.

When another possibility can to determine the water content data are used, the properties of fluorescence radiation from that to be ablated Area of the body emanates. The creation device can for this purpose preferably a for transmission of detected fluorescence radiation data via a data link with the device connected to the data processing device for detection of fluorescence radiation, which upon irradiation of the ablatierenden surface of the body of Material on the surface of the body is discharged, and wherein the data processing device preferably to determine the water content of the material depending on is formed by the fluorescence radiation data. The fluorescence radiation can either by irradiating the area to be examined of the body with a radiation source not used for ablation, or as far as possible, by irradiation with laser radiation used for ablation Lasers be stimulated. This alternative is characterized from that the instrumental requirements for performing the measurement relatively low can be kept.

Yet one more way is to use data to determine the water content, the reflect the refractive index in the material. Preferably the creation device for determining the refractive index of Materials an optical coherence tomography have, for transmission of measured data over a Data connection connected to the data processing device is. This exploits that the refractive index of the material depend on the water content can. An advantage of this variant may be that the optical coherence tomograph also for Topography measurements can be used on the surface of the body. The coherence tomograph can be further used to advance the thickness of the cornea and / or while to determine the ablation, i. to perform a pachymetric measurement. In order to can be avoided in particular that during ablation, the residual thickness the cornea falls below a predetermined minimum value.

The consideration The water content can be done in different ways. So can For example, modified known creation method to this effect be that in these models for the Ablation can be used, which take into account the water content. However, this may require a redesign of these procedures.

In another possibility, it is therefore necessary to create the ablation program to be used preferably that, in order to take into account the water content from the predetermined target ablation profile, a ablation profile precompensated depending on the water content is determined, and the ablation program is created from the precompensated ablation profile. The target ablation profile is preferably modified so that the ablation leads at least approximately to the desired target ablation profile in accordance with the ablation program created on the basis of the modified target ablation profile. In particular, a simple generation method can be used to create the ablation program from the modified or precompensated target ablation profile. In the context of the present invention, a simple creation method is understood as meaning a creation method which does not take into account the water content of the material when the ablation program is created. The errors that occur when using a simple creation method for creating an ablation program by disregarding the water content, can be compensated by a corresponding modification of the target Ablationsprofils, that is, the output data for creating the Ablationsprogramms so that subsequently a simple creation method can be used. The type and scope of the precompensation or modification may depend on the properties of the simple creation method used or on the model assumptions on which it is based. The modification thus changes the target ablation profile by way of a precorrection or precompensation in such a way that deviations between the desired ablation depth and the actual ablation depth, which do not take into account the water content of the material in the creation of an ablation program with a simple predetermined creation method the water content is not taken into account, can be precompensated by changing the predetermined target Ablationsprofils in the opposite direction or size. This embodiment has the advantage that simple creation methods can be used to create the ablation program to be used, so that already proven methods can be used. Examples of such simple creation methods are in DE 197 27 573 C1 or EP 1060710 A2 described, the contents of which are hereby incorporated by reference in the description.

To it is preferred that Determination of the precompensated ablation profile a modification function that is used explicitly or implicitly by the water content depends on the material to be ablated. In particular, for at least two areas of the surface to be ablated each have a value of a modification function dependent on of at least the water content of the material at the surface in the determined area and the modified or precompensated Target ablation profile using the desired ablation profile and the values of the modification function are determined. The creation The ablation program can be characterized in particular by a simple Creation process. The values of the modification function are preferably for every pulse or for every place on the surface, on which a pulse is to be directed, calculated. The values can be for everyone Area or destination respectively recalculated. However, it is also possible, to calculate the throw only once and then in a table, for example dependent on from the water content or any size dependent on it, from which they then each can be read when needed. This procedure allows a particularly simple determination of the precompensated target ablation profile. The modification function can be explicit from the water content of the material at the destination or implicitly over at least one other Depend on the parameters of the modification function.

The In particular, modification function can be performed using the above mentioned Model for by a single pulse depending on the water content achieved ablation depth or by a single pulse depending Ablation volume achieved by the water content and optionally the further model for the change the water content determined by ablation and be this included.

Preferably depends on that Modification function of intensity, energy or fluence the pulse to be used during ablation. Here, the modification function also from a threshold for depend on the energy or effective fluence, which indicates from which Energy or effective Fluence ablation of the material occurs and which preferably depends on the water content in the material. Especially For example, the modification function of the dimensionless ratio of Fluence and the fluence threshold depend.

During ablation, the water content of the material may change due to the pulses that have already hit the body. Since it may be necessary to deliver multiple pulses to a target site to achieve a desired depth of ablation, it is preferred in the method of construction that the value of the modification function at a particular given location depends on a desired ablation depth given by the target ablation profile at the location. This has the advantage that in a simple way the dependence on the water content of the material even for large ablation depths be easy before the actual ablation can be considered. The modification function may still depend on at least one further parameter, which in particular itself depends on the water content present in the material or the change in the water content due to the impingement of a pulse.

Farther It can be cheap prove that out A preliminary ablation program is created for the desired ablation profile and the formation of the ablation program to be created depending on at least one of the water content by the preliminary ablation program implicitly or explicitly specified fluence value or a by the provisional Ablation program implicitly or explicitly given pulse energy of a on one by the provisional one Ablation program given destination to be delivered pulse in dependence changed from the water content at the destination and as an indication of the destination is assigned. The preliminary Ablation program can be used with any creation method In particular, a simple creation process can be created can be used from the specified target ablation profile without the consideration the water content of the material creates the preliminary ablation program. However, it is also possible a preliminary one Ablation program, for example, under an approximate way or simplified consideration of the water content and this then by change nachkorrigieren the pulse energy or the fluence value. In the Determination of the change the fluence value or the pulse energy can therefore be considered in particular which assumptions or models are used to prepare the preliminary ablation program were used.

The change In particular, the fluence value can be determined using the above mentioned Model for by a single pulse depending on the water content achieved ablation depth or by a single pulse depending determined by the water content Ablationsvolumen determined or derived be and contain this insofar.

The Setting the energy or fluence of a pulse can be up at least three ways, alternatively or in combination can be applied. In a first variant is used to adjust the energy or Fluence of a pulse of the laser beam attenuated. This is preferably done a control signal is formed, by means of which one for ablation used laser beam debilitating Modulator is controllable in its transmission. The control device is for this purpose preferably for the formation and delivery of control signals for controlling a modulator which weakens the laser beam according to a developed ablation program trained. The laser ablation device has in addition to the control device with a control device connected modulator on which the laser beam on control signals the control device weakens. As a modulator can serve any device with which the intensity of the laser beam emitted from the laser can be reduced. For example, you can Pockels cells, controlled by a drive rotatable glass panes, with radial sectors of different transmissivity or liquid crystal elements be used with controllable transmissivity. The modulator can act, for example, polarization-dependent or wavelength-dependent. The use of modulators allows easy adjustment the pulse energy for any type of laser.

at The second variant can be used to adjust the energy or fluence a pulse used to deliver the pulsed laser beam Be controlled laser. You can do this Control signals for driving the laser of the laser ablation device are formed, by means of which the Fluence or pulse energy of the pulse delivered to the laser is controlled. The control device can be used to generate and output control signals Control of the laser according to a be formed ablation program. In the laser ablation device then preferably the laser is controllable by means of the control device. When using excimer lasers, the control device can in particular the high voltage to charge a capacitor or more Capacitors for storing energy for generating a laser pulse Taxes. The control of the pulse energy or fluence of the laser has the advantage that less Energy needed becomes.

When third variant can be used to adjust the fluence of a pulse Beam cross section of the laser beam to be changed at the surface. For this purpose, control signals for controlling a beam-shaping optical device in the beam path the laser beam, which serves to adjust the beam cross section, according to one created ablation program and to the beam-forming optical device are issued. The control device can according to the formation and delivery of control signals for driving a beam-shaping optical device in the beam path of Laser beam, which serves to adjust the beam cross section, according to a be formed ablation program. A laser ablation device For this purpose, a corresponding in the beam path of the laser beam have arranged beam-forming optical device, the of the control device for modification of the beam cross section is driven.

One Ablation program, in particular an ablation program in which the Fluence or energy of the pulses used can be changed before the actual Ablation to be created. However, it is in the control signal forming method preferred that after the preparation of a first part of the ablation program and delivery corresponding control signals at least one more still abarbeitender Part of the ablation program and generates appropriate control signals be delivered. this makes possible it is advantageous to start ablation while that full Program is still being created, so the time between deployment of the desired ablation profile and end of the ablation is shortened.

Furthermore allows it is a particularly preferred embodiment of the Steuerignalbildungs- and delivery method, starting from the target ablation profile a preliminary one Ablation program is created and used to create at least another part of the ablation program for at least one by the provisional Ablation program given destination on the surface of the Water content is determined, and the preliminary ablation program under Formation of the ablation program as a function of the determined Changed water content becomes. This has the advantage of being a change the water content during the Ablation, for example due to environmental influences or by preceding ablation on the same or an adjacent one Place can be caused while still the ablation can be taken into account. It can in particular the provisional Ablation program already considering one example created as a statistical average corresponding water content be individual variations of the water content during the Ablation considered become. Preferably, the preliminary ablation program is changed the fluence or pulse energy to be delivered at least in explicit or implies dependency transferred from the water content in the ablationsprogramm to be processed or used.

Especially in the last described embodiment it is preferred that during the Delivery of control signals by measurements on the body data detected which reflect or exclude the water content of the material where the water content of the material can be determined. For this purpose can the creation device over a control interface the means for measuring the data automatically drive.

In the creation of the ablation program, further influences can be taken into account, in particular in the case of known creation methods, as described in US Pat DE 197 27 573 C1 or EP 1060710 A2 are not considered. Thus, it is preferable that the ablation program is also prepared depending on the air humidity of the air at the surface and / or the thickness of a liquid film on the surface. This development has the advantage that also influences are taken into account that indirectly influence the water content in the material. In addition, the thickness of the liquid film on the surface can affect the effectiveness of the ablation if the liquid film need not be vaporized by the pulses before the ablation of material. Both the humidity and the thickness of the liquid film may be measured before or preferably during ablation and taken into account in the creation of the ablation program. For this purpose, the creation device preferably has an interface for reading in data representing the air humidity or the thickness of the liquid film, and particularly preferably a device for measuring the data representing the air humidity or the thickness of the liquid film. As a result, a particularly compact construction is achieved in an advantageous manner and enables automatic measurement.

Further, it is preferable that the ablation program is also prepared depending on a shape of a beam profile of the laser beam and / or a tilt of the surface. The inclination of the surface is preferably given at least approximately relative to the laser beam. If the laser beam is only tilted by small angles, for example less than 5 °, it is possible, for example, to select a mean position of the laser beam as the reference direction relative to which the inclination is determined. This development is based, inter alia, on the idea that the energy actually effective for the ablation per area, that is the actual effective fluence, of a pulse of the pulsed laser beam impinging on the surface of the body does not depend solely on the inclination of the surface relative to the direction of the Laser beam depends on the surface, but also on the beam profile of the laser beam, in particular on the surface of the body. In this case, the course of the beam is understood to mean the course of the intensity or the energy or fluence of the pulse, which is related to the area, across the beam cross section near the surface. The shape of the beam profile does not include any absolute values of the intensity or the energy or the fluence related to a cross-sectional area perpendicular to the laser beam, but only the course of these quantities. In particular, the method is therefore suitable for ablation with laser beams with a non-constant beam profile. This variant of the method has the advantage that even strongly curved surfaces can be ablated with high accuracy by means of a laser beam, which in particular need not have a constant beam profile. The surface data necessary to create the ablation program, from which the Slope, it is possible to indicate directly the slope of the surface as a function of location, the gradients of the height of the surface above a given reference plane in which the locations are indicated, or also the heights of the surface above the reference plane as a function of the location In particular, the display options mentioned in relation to the desired ablation profile can also be used. If these data do not explicitly contain the slope, for example given by corresponding angles, this information can be easily determined by gradient formation and / or the use of trigonometric relationships.

ever after application can in the data processing device, the desired ablation profile and / or the Data related to surface tilt be stored, which in particular offers, if several same body to be ablated one after the other. Can also the surface data change with respect to the inclination of the surface, the inventive construction device continue over one Interface for capturing surface data that the inclination of the surface play directly or indirectly. The interface can be like that Interface designed to detect the desired ablation be. Preferably, the surface data is automatically detected, including the data processing device has a corresponding control interface for issuing control commands to a device for detection of surface data can have.

The In particular, the creation device can be a device for detecting of surface data a topography measuring system for detecting the topography of the surface and / or an aberrometer for detecting optical properties of the body. This training has the advantage that one simple and accurate recording of the surface topography of the ablatierenden surface without an additional Alignment of the coordinate systems in which the slopes or surface topography data and the target ablation profile and, where appropriate, the water content data are given is, as the Topographiemeßsystem is held in the device.

The consideration the slope of the surface and / or the shape of the beam profile can be achieved in particular be that to consideration the shape of the beam profile and / or the inclination of the surface the desired ablation profile using a modification function, which depends on the shape of the beam profile and / or the inclination of the surface in terms of influences the shape of the beam profile and / or the inclination of the surface precompensated Target ablation profile is determined, and that from the determined in relation on influences the shape of the beam profile and / or the inclination of the surface precompensated Target ablation profile the ablation program is created. To create of the ablation program from the in terms of influences of Precompensated shape of the beam profile and / or the inclination of the surface Target ablation profile can In turn, the creation process uses a dependency the shape of the beam profile and / or the inclination of the surface is not consider. In this way, a compensation of Errors occur by means of a precorrection or precompensation, in which the target ablation profile is modified in such a way that errors, by using a build process that has a dependency the shape of the beam profile and / or the inclination of the surface is not considered, occur during ablation according to the ablation program at least in a good approximation repressed become. Preferably contains the modification function influences both the water content as well as the surface inclination and the shape of the beam profile. This may cause the creation of the ablation profile be simplified in an advantageous manner.

to Creation of the ablation program is suitable for a computer program with program code to perform the inventive creation method, when the program is running on a computer.

Furthermore the subject of the invention is a computer product with program code, stored on a computer-readable medium to the inventive preparation method perform, when the computer program product is running on a computer. Under a disk In this case, any data carrier is understood, in particular a magnetic data carrier, such as a floppy disk or hard disk, a magneto-optical disk, an optical disk such as a CD, DVD or Blue-Ray disc, or even a other non-volatile Memory, such as a so-called flash ROM.

In this case, a computer means any data processing device, in particular a data processing device of the creation device, with which the method can be executed when the program is executed thereon. In particular, this may comprise a digital signal processor and / or a programmable microprocessor, with which the method in whole or in part is performed. The processor may be connected to a memory device in which the computer program and / or data for executing the computer program are stored.

The The invention may be advantageous for ablation of a desired ablation profile of biological material, in particular the cornea in the case of laser surgery Treatment of a refractive error of the human eye, for example with PRK, LASIK or LASEK.

The Invention will be described in more detail by way of example with reference to the Drawings explained. Show it:

1 a schematic perspective view of a patient during a treatment with a laser surgical instrument with a laser ablation device with a signal-generating device according to a first preferred embodiment of the invention,

2 a schematic block diagram of the laser ablation device in 1 .

3 a schematic representation of a spherical body to be machined and a coordinate system used in a Ablationsprogramm creation method,

4 a schematic representation of a section through a desired Ablationgsprofil along a diameter through the body in 3 and single-pulse ablation volumes,

5 a flowchart of a method for forming control signals according to an ablation program for the instrument created in the method in 2 according to a first preferred embodiment of the invention,

6 3 is a flowchart of a method for generating and outputting control signals according to an ablation program created in the method according to a second preferred embodiment of the invention,

7 a flowchart with partial steps to step S28 from the flowchart in 6 .

8th 1 is a block diagram of an ablation device with a signal-generating device according to a third preferred embodiment of the invention for a laser-surgical instrument;

9 a block diagram of an ablation device with a signal-generating device according to another preferred embodiment of the invention, and

10 a flowchart of a method for generating and outputting control signals according to an ablation program created in the method according to the further preferred embodiment of the invention.

In 1 is a laser surgical instrument 1 for the treatment of an eye 2 of a patient used to perform a refractive correction of the eye. The instrument 1 gives it a pulsed laser beam 3 on the eye 1 of the patient, whose head is in a head holder 4 who is stuck with the instrument 1 is connected, is fixed.

2 schematically shows in more detail the structure of the instrument, which represents a laser ablation device. The instrument comprises a data processing device 5 with an integrated control device 6 , one from the controller 6 controlled laser 7 and a likewise controlled by the control device deflection 8th , by means of which of the laser 7 emitted pulsed laser beam 3 according to a predetermined ablation program on target sites on the cornea of the eye 2 can be directed and focused.

The instrument also has a device 9 for the acquisition of water content measurement data, from which the water content of an area of the eye to be treated 2 , More specifically, the cornea or cornea, can be determined, and a device 10 for determining a desired ablation profile. Both devices are with the data processing device 5 connected. The data processing device 5 , the control device 6 , the device 9 for acquiring water content measurement data and the facility 10 to determine the Target ablation profiles form a device for creating an ablation program according to a first preferred embodiment of the invention.

The data processing device 5 with the integrated control device 6 is used to create an ablation program using data from which the water content in the material of the area to be treated can be determined from data relating to properties of the laser beam 3 and data related to the target ablation profile to be ablated. The data processing device 5 For this purpose, it has a processor and a memory for storing data, in which in particular a computer program with program code is stored, by means of which, when the program is executed on the processor, the ablation program is created and the integrated control device is used 6 Control signals for driving the laser 7 and / or the deflector 8th formed and attached to the laser 7 or the deflection device 8th delivered to perform the actual ablation. The memory and the processor are partially represented in the block diagram by the block "Creation of the ablation program".

The data processing device 5 has interfaces for data input, namely an interface 11 for reading water content measurement data from the device 9 for acquiring water content measurement data, an interface 12 for manually entering the desired ablation profile and an interface 12 ' for reading data relating to the desired ablation profile from the device 10 for determining the desired ablation profile. In addition, an interface 13 for entering beam parameters for the laser beam 3 intended. In this embodiment, the interface 13 designed as an interface for manual input.

at the interfaces for a manual input can be a physical one single interface to which, not shown in the figures, a keyboard and a monitor on which an input prompt can be displayed is, if appropriate data is to be read, attached are. The interfaces further comprise corresponding modules of the Computer program for reading the data from the keyboard.

The other interfaces 11 ' and 12 ' are conventional interfaces for data streams, which also include software modules in addition to corresponding electronic modules.

The control device 6 is in the data processing device 5 integrated and further has not shown in the figures interfaces for the delivery of control signals for driving the laser 7 and the deflector 8th , Such control devices are basically known and therefore need not be explained in detail.

The laser 7 is with the control device 6 connected and depending on the Ablationsprogramm a pulsed laser beam with predetermined pulse energies from. For example, an eximer laser having a wavelength in the wavelength range of 193 nm can be used.

The deflection device 8th is also via a data connection to the controller 6 connected and steered accordingly control signals from the controller 6 according to the ablation program to be processed by the laser 7 emitted, pulsed laser beam 3 on predetermined destinations on the surface of the eye 2 , For this purpose, has the deflection 8th via a focusing device 14 for focusing the laser beam along its propagation direction and for deflecting transversely to the laser beam via two mutually orthogonal to each other extending axes rotatable or pivotable mirror 15 in the beam path after the focusing device 14 are arranged.

Both with the laser 7 as well as at the deflection device 8th they may be conventional, known devices of a laser surgical instrument.

To indicate the water content and the desired ablation profile, two parallel Cartesian coordinate systems are used whose xy planes coincide. The z-axis is aligned as far as possible in a good approximation parallel to the optical axis of the eye. The example assumes that the origins of the coordinate systems coincide so that the coordinate systems coincide and are no longer distinguished. If the coordinate origins do not coincide, the relative position can be entered manually after reading in the water content or the desired ablation profile, whereupon the data can be converted into a common coordinate system. To enter the relative position then a corresponding interface can be provided. In 3 is the position of the coordinate system for a spherical body or a sphere with a surface 2 ' as a simplified model for the eye 2 shown. The determination of the z-axes takes place during the alignment of the eye 2 relative to the instrument 1 for which purpose, for example, a fixing light not shown in the figures can be used.

The device 9 For recording water content measurement data in the example comprises a device for confocal Raman spectroscopy of the cornea of the eye, as described for example in "Assessment of Transient Changes in Corneal Hydration Using Confocal Raman Spectroscopy", Brian T. Fischer et al. Cornea 22 (4), pages 363-370, 2003. The treatment area of the cornea of the eye 2 is scanned with a suitable laser beam, which is focused both in depth and laterally to the laser beam. From the eye 2 Outgoing Raman radiation is then detected confocally, so that for different locations in the volume to be ablatierten the intensity of. Raman radiation can be detected. The intensity rendering data, ie the water content measurement data, will be transmitted over the interface for each measured location 11 in the data processing device 5 read. The computer program in the data processing device 5 has program code, by means of which the data in the water content at the respective place descriptive data can be converted.

The device 10 To determine the desired ablation profile comprises in the present example, a wavefront analyzer Hartmann-Shack type and optionally means for determining the refractive power of the eye 2 from which or by known methods a target ablation profile D _desired for the area of the eye to be treated 2 can be determined. The target ablation profile is determined so that the greatest possible correction of aberrations by the eye 2 can be achieved by the still to be performed ablation. An example of the target ablation profile is 3 removable. It is through the distances in z direction between the initial surface, the ball cap 2 ' , and a desired surface 2 '' , indicated by a dashed line, given as a function of location in the xy plane. An area to be ablated is defined by the volume between the surface 2 ' before the ablation and the desired surface 2 '' formed, which is formed by the desired Ablationsprofil.

To determine the desired Ablationsprofils the device 10 have an appropriate processor that records the data regarding the refractive power of the eye 2 and evaluates the wavefront data, in turn in the present example in the form of target ablation depths for support points in the form of points of a point grid in the xy plane of the corresponding coordinate system which coincides with the xy plane of the coordinate system for indicating the desired ablation profile determine. As far as the coordinate origins do not match, the position of one of the reference points or coordinate origins in the other coordinate system can be specified so that the data can be transformed by a simple shift in the same coordinate system in the later course of the procedure. This may prove beneficial if the center of the target ablation profile, that is, a point relative to which the target ablation profile is approximately symmetrical, is from the center of the surface of the eye 2 that is, a point relative to which the surface of the eye is approximately symmetrical. A method for producing a desired ablation profile is described, for example, in WO 01/08075 A1, the contents of which are hereby incorporated by reference into the description.

The A method of creating an ablation program of the first embodiment based on the following considerations.

To the target ablation profile D _target of the eye 2 to ablate, according to a created ablation program on predetermined destinations on the eye 2 Laser pulses given a predetermined pulse energy, each individually lead to a removal of material. The depth of erosion by a pulse can be described by various models. In the present example, the so-called "blow-off" model is used, for example, in "refractive surgery of the cornea", publisher Theo Seiler, 1st edition, ENKE Georg Thieme Verlag, Stuttgart / New York, 2000 (ISBN 3-13 -118071-4), Chapter 6.1, p.150 or in R. Srinivasan: "Ablation of Polymers and Biological Tissue by Ultraviolet Lasers", Science vol. 234, p.559-565, Oct. 31, 1986.

Thereafter, at a location with the coordinates (x, y) by a laser radiation incident at this location with an effective fluence F (x, y), that is energy per area, material is removed to a depth D _P according to the following formula:

In this case, μ denotes a material-dependent ablation coefficient and F _thr also a material-dependent ablation threshold value for the fluence, below the laser radiation of which there is no removal of material from the eye 2 causes more.

at the simple method of creating an ablation program used in the following It is assumed that the Target ablation profile in single-pulse ablation volumes that are incident upon impact of a pulse, can be decomposed. The creation of the Ablation program then includes the determination of the destinations (x, y) are directed to the pulses of a given pulse energy have to.

To create an ablation program, it is assumed that a laser pulse ablates a single- _pulse or spot ablation volume V _pulse , which results as the integral of the ablation depth D _P over the entire pulse area:

The integral extends over the area designated "Spot" in which D _P > 0.

In the following it is assumed that the area in which D _P > 0 is constant and has an area d ² . It is then V _pulse = d ² D _P.

In the case of simple preparation methods in which the water content of the material to be ablated and in particular variations in the water content of the material to be ablated are not taken into account, the result for the ablation depth D _{P, 0} for a pulse without consideration of the water content is:

Μ ₀ denotes an empirically determined ablation rate assumed to be constant. The empirical determination can be determined by examining the ablation on a larger number of different eyes, or their cornea.

Using a simple method of creating an ablation program, it is assumed that each pulse delivered to the same location ablates the same single pulse volume or Pp ₀ ablation, the volumes adding up. This is in 4a illustrated. In this figure is a schematic example of a target ablation profile along a diameter through the eye 2 , shown approximately along the x-axis. The single-pulse ablation volumes V _S are successively ablated and produce the desired ablation depth, each individual-pulse ablation volume V _S corresponding to a single-pulse ablation depth D _{P, 0} . If the coordinates of the destinations under consideration are denoted by (x _i , y _i ), i = 1,..., G, G is a natural number, the number N _{i, 0} of a destination (x _i , y _i ) pulses to be delivered:

wobei die vom Wassergehalt H abhängige Ablationsrate μ(H) beispielsweise als proportional zu dem Wassergehalt H mit einer Proporfionalitätskonstanten k angenommen werden kann: μ(H) = k·H. (6) In fact, however, the ablation rate μ depends on the water content H in the material to be ablated. In a simple model based on the blow-often model, in the example, the single-pulse ablation depth D _{P, W} results for one pulse taking into account the water content of the material

wherein the ablation rate μ (H) dependent on the water content H can be assumed, for example, as proportional to the water content H with a proportionality constant k: μ (H) = k × H. (6)

The value of the proportionality constant k is selected such that the mean water content H _{m of} the cornea k · H _m = μ ₀ determined in the above-mentioned series investigations applies.

In fact, however, the water content of the ablatierenden material or tissue of the Cor Change nea depending on the ambient conditions such as humidity, air flow over the eye, air temperature and the Ablationsbedingungen, such as the Ablationsrate, the number of pulses to a destination (x _i , y _i ) or in the vicinity of his pulses and the fluence of the pulses , In this exemplary embodiment, the following model is assumed for the water content H of material to be ablated above a target location (x _i , y _i ) to which n (x _i , y _i ) pulses have already been emitted: H (x i , y i N (x i , y i )) = a (x i , y i ) + b · log (n (x i , y i )). (7)

The parameter a describes the water content at the target location (x ₁ , y _i ) before the beginning of the ablation. Among other things, this water content may depend on the type of treatment, for example photorefractive keratectomy, LASIK, LASIK with photodispruptive formation of a fold-down corneal cap or LASEK, the properties of the individual eye and the environmental conditions prior to ablation. The parameter b assumed to be constant in this embodiment describes the change in the water content by delivering pulses to the location (x _i , y _i ). In particular, the parameter b can be obtained empirically by screening.

When delivering N _{W, i} pulses to the same target location (x _i , y _i ), the single-pulse ablation depths, which are now no longer constant as a function of the water content H, add up to a total depth. The number of N _{W, i} can be determined so that the target ablation depth D _target (x _i , y _i ) at the location (x _i , y _i ) is just reached:

As shown in equation (8), can when dispensing a large number from pulses to the same place the sum is approximated by an integral be replaced to approximate the sum, but to calculate faster.

As the rate of ablation increases as the number of pulses increases, the actual ablation depth on delivery of N _{W, i} pulses to the location (x _i , y _i ) varies with each pulse and differs from N _{i, 0} times the single pulse Ablation depth D _{P, 0} in the simple model, which does not take into account the water content.

In order to be able to use a simple, for example, known creation method in which the water content is not taken into account, a modification function M is defined for calculating a pre-compensated or modified target ablation profile D _Mod from the predetermined target ablation profile D _target serves: D Mod (x i , y i ) = M (D Should (x i , y i )) D Should (x i , y i ) (9) With

As expressed in formulas (9) and (10), the modification function depends on the target ablation depth D _target (x _i , y _i ), the parameter a and thus the water content of the material before ablation and the parameter b and thus the Change in water content due to ablation. In addition, there is a dependency on the model used in the simple construction method for D _{P, 0} .

Especially can the ablation effect of a single pulse with increasing number increase the delivered to the same place pulses, so that at a huge Target ablation depth, which is a larger number of Single pulses to the same place requires less individual pulses to be used as according to the formula (4) is to be expected.

Now, if a simple creation method for creating the ablation program from the precompensated target ablation profile D _{mod is} used, the factor M contained in D _Mod compensates precisely for the errors that arise because the water content in formula (3) is not taken into account Ablation with a created by the simple method of preparation of the pre-compensated target ablation ablation program in good approximation, the predetermined target ablation profile is achieved.

In order to determine the locations to which laser pulses are to be output, various known simple generation methods can be used, for example those in DE 19727573 C1 and EP 1060710 A2 described method. In DE 19727573 C1 the ablation is carried out in layers, that is, locations of impingement are determined in layers by pulse, the desired profile then being obtained by superposition of these layers. In the method in EP 1060710 A2 The spot distance is varied quasi-continuously to achieve the desired ablation depth.

To determine the ablation program, those shown in the flowchart in FIG 5 sketched method steps carried out, including the computer program executed in the data processing program corresponding program code.

First, in step S10, the target ablation profile D _target is determined using the device 10 determined to determine the desired ablation profile. This determination is triggered here by a user. In another embodiment, the data processing device is 5 via a control interface, not shown in the figures, a corresponding control signal to the device 10 to determine the target ablation profile to start the determination automatically. For determination, aberrations are determined from wavefront data. With known methods it is calculated at which points of the surface of the eye material is to be removed to what depth. In the present example, the target ablation profile D _{target is given} by specifying the target ablation depth as a function of location on a grid in the xy plane.

This data is then passed through the interface in step S12 12 ' in the data processing device 5 read in and stored there in their memory.

In the example after steps S10 and S12, in other embodiments but also before these steps, spatially resolved intensities of Raman radiation are detected as Wassergehaltemeßdaten in step S14 by means of confocal Raman spectroscopy and these intensities reproducing data together with corresponding location coordinates to the data processing device 5 Posted. This determination is triggered here by a user. In another embodiment, the interface 11 also designed as a control interface and the data processing device 5 gives about this control interface 11 a corresponding control signal to the device 9 to start the discovery automatically.

In step S16, the water content measurement data is transmitted via the interface 11 read in and in the memory of the data processing device 5 cached. Water content values a are then determined from the intensities for all locations for which water content measurement data were recorded and assigned to the locations.

In step S18, then via the interface 13 Beam parameter of the laser beam to be used 3 read. In this embodiment, the diameter beam profile of the laser beam is to 3 entered. The shape of the laser beam 3 is assumed to be constant across the beam cross-section and fixed and is in the form of corresponding formulas in that on the processor of the data processing device 5 the current program. Furthermore, the pulse energy to be used per area or the fluence F ₀ to be used is read in and stored.

In step S20, a pre-compensated desired ablation profile D _Mod is then determined from the predetermined desired ablation profile D _Soll . For this purpose, the following two partial steps are carried out for all support points at which the desired ablation profile is given: Values for the proportionality constant k and the threshold value for the fluence F _thr are stored in the program code. If (x _i , y _i ) _denotes the location, the equation given by the formula (8) is determined using the target ablation depth D _target (x _i , y _i ) given by the target ablation profile and the values a (x _i , y _i ), b, k and F ₀ / F _{thr are} solved, for example, by means of a Newton method for the solution of nonlinear equations for the number of pulses N _{W, i} . If a is not present at the location (x _i , y _i ), a corresponding value can be obtained by interpolation. Then, the value M (D _target (x _i , y _i )) of the modification function M is determined according to formula (10).

In the following sub-step, in order to form a pre-compensated setpoint ablation depth D _Mod at the location (x _i , y _i ), the predetermined target ablation depth D _setpoint (x _i , y _i ) with the value M (D _setpoint (x _i , y _i )) of the modification function multiplied and stored as D _mod (x _i , y _i ) associated with the location (x _i , y _i ).

The precompensated target ablation profile D _Mod is then given by the locations (x _i , y _i ) and the pre-compensated target ablation depths D _mod (x _i , y _i ) associated therewith.

In the following step S22, an ablation program is prepared on the basis of the modified target ablation profile D _Mod , the read fluence and the other beam parameter and formula (3) using a method which therefore does not alter the water content of the tissue or the change the water content of the tissue during ablation. For example, this can be done in DE 19727573 C1 described method can be used. The ablation program created in this way comprises a sequence of target locations in the xy plane, that is to say corresponding coordinates, to which laser pulses with the pulse energy determined by the read-in fluence must be directed in order to achieve the desired target ablation profile. The ablation program is in the data processing device 5 saved. This step completes the actual creation of the ablation program.

In the following step S26 are then from the data processing device 5 with the integrated control device 6 Control commands to the laser 7 and the deflector 8th delivered according to the created ablation program material from the eye 2 ablate.

The Ablation procedure is suitable for photorefractive keratectomy as well as LASIK. Because in this process material in different Layers of the eye is removed accordingly, if necessary different target ablation profiles are used.

A second embodiment of a method for forming and delivering control signals for ablation according to an ablation program created by the method is disclosed in US Pat 6 and 7 shown. A corresponding signal-forming device differs from the signal-forming device of the first embodiment only in the programming of the data processing device 5 and only in that it can perform the method described below for the formation of control signals or for the preparation of an ablation program. The method differs from the first method essentially in that now the Fluence is changed by pulses of the pulsed laser beam according to the water content, which also occurs during the delivery of the control signals and thus the ablation.

The method of forming and outputting control signals, which includes the method of creating an ablation program, has some steps similar to those of the methods described in 5 correspond to the signal forming or creation method illustrated. These are therefore denoted below by the same reference numerals and will not be described again.

In Steps S10 and S12 or S14 and S16 thus become data the desired ablation profile or the water content of the corneal tissue determined and stored before ablation.

In the subsequent step S18, a beam cross-section and a preset initial fluence value F _{0 are} read.

In the following step S26, a preliminary ablation program is then prepared on the basis of the read-in target ablation profile, the read preset fluence and the beam parameter, the simple method of preparation used for this purpose not taking into account the water content of the cornea or variations of the water content. In particular, the above-mentioned method can DE 197 27 573 C1 be used. The preliminary ablation program, in turn, consists of a series of coordinates for locations on the surface of the eye 2 to which pulses are to be steered comprises is then stored.

Thereafter, in step S28, modified fluence values are obtained from the sequence of destinations corresponding to the preliminary ablation program for the respective pulses and assigned to the target locations to form the ablation program to be used. After the formation of a modified fluence value, a control signal is formed directly and sent to the laser 7 or the deflection device 8th issued. By appropriate control of a high voltage power supply of Eximerlasers 7 and thus the charging of capacitors, in each of which the energy is stored for a pulse, according to the Ablationsprogramm and simultaneous control of the deflector 8th The ablation can be carried out with a laser pulse with a location-dependent or coordinate-dependent pulse energy and thus fluence.

The succession of the destinations will be successively processed. The corresponding sub-steps for determining a changed fluence a pulse to be delivered to a destination (x _j , y _j ) are in 7 shown.

In sub-step S28a, the first destination is first read in the first pass, and the next destination in later runs is read out according to the preliminary ablation program. This has the coordinates (x _j , y _j ), where j is the ordinal number of the destination in the sequence.

In sub-step S28b is then by driving the device 9 for acquiring water content measurement data by the data processing device 5 via a control interface, not shown, a detection of corresponding data for the destination (x _j , y _j ) carried out.

The data is sent via the interface 11 read in and converted in sub-step S28c by means of the Datenverarbeitunseinrichtung in a water content H (x _j , y _j ) at the destination (x _j , y _j ).

In sub-step S28d, a changed fluence value is then determined for the pulse to be output to the destination location (x _j , y _j ), which is assigned to the destination. The changed fluence value together with the target location (x _j , y _j ) forms an element of the finally to be used ablation program.

The fluence value is then changed to achieve the single-pulse ablation depth when ablation with the altered fluence, which was assumed to be the ablation depth for a single pulse when the preliminary ablation program was established without consideration of water content. Starting from equations (1), (3) and (4) given above, the equation D _{P, W} (F) = D _{P, 0} (F ₀ ) must therefore be solved for F, where D _{P, W} over μ ( H) depends on the water content H at the destination. Using the models according to equations (1), (3) and (4) one obtains the following equation for the changed fluence:

These Calculation can be done very quickly, so that the sub-step S28d can be run through very quickly.

It can be appropriate control signals for the laser 7 and the deflector 8th formed and attached to the laser 7 ie the high voltage supply of the laser 7 , or the deflection device 8th be delivered. Thereafter, the process continues with sub-step S28a for the next element of the preliminary ablation program. The steps S10 to S28d without the formation and output of the control signals form, as before, steps S10 to S22 an embodiment of a construction method according to the invention.

In order to need up to the model for the ablation depth, no assumptions about the water content of the cornea to be met. In particular, even unforeseen changes the water content during the formation and delivery of the control signals and thus the ablation fully considered become.

A third embodiment, which is a variant of the previously described embodiment, is shown in FIG 8th shown. The instrument shown here schematically differs from the instrument of the preceding embodiment in that in the beam path of the laser beam 3 between the laser 7 and the deflector 8th a modulator 16 in the example one from the control device 6 ' in its transmission controllable liquid crystal element is arranged. In addition, the control device 6 ' opposite the control device 6 an output for controlling the modulator 16 on and in the data processing device 5 processed computer program is not to control the Fluence by driving the laser 7 but by changing the transmission of the modulator 16 educated.

The fluence of the laser 7 is now set so that at maximum transmission of the modulator 16 the maximum required fluence for ablation can be achieved according to the ablation program. The modulator 16 is controlled during ablation in accordance with the ablation program so that the pulses impinging on the surface have the desired energy or fluence.

In another variant, instead of the modulator 16 a beam-shaping device may be provided, which changes the beam cross section and thus the fluence to signals from the control device.

In other embodiments of the methods described above, the ablation threshold F _thr for the fluence may also depend on the water content H.

In a fifth preferred embodiment of a control signal generation method of the invention, equation (9) is used directly in the creation of the ablation program by specifying a pattern of target locations and solving equation (9) for each target location as a function of the number of pulses N _{W, i to} be delivered becomes.

In a sixth preferred embodiment of a control signal formation method, in addition to the water content, the inclination of the surface of the cornea with respect to the laser beam also increases 3 or the z-direction as an approximation for the direction of the laser beam 3 considered in conjunction with the actual shape of the beam profile. The one from the laser 7 emitted laser beam 3 in the example has a beam profile with Gaussian shape.

Whereas in conventional methods the effective fluence F (x, y) is assumed to be constant over the area of the pulse or spot, two further influences are taken into account simultaneously with the influence of the water content. On the one hand, it is considered that due to the inclination of the surface to be machined, the effective fluence corresponds to the inclination to the fluence of the laser beam 3 is lowered. If the surface to be machined is described by a height function f (x, y) indicating the height of the surface above the xy plane, the inclination angle θ of the surface relative to the z-axis may be approximately that of the surface 2 ' incident laser beam 3 according to the formula θ (x, y) = arctan (| grad f (x, y) |) (12) be determined. The effluent F (x, y) on the surface which is effective during the ablation thus results F (x, y) = F P (x, y) · cosθ (x, y) (13) where F _P (x, y) the fluence at normal incidence of the laser beam 3 to the surface, ie at an angle θ = 0. F _P therefore corresponds to the fluence or the beam profile of the laser beam 3 ,

As the second effect, it is considered that the effective fluence corresponding to the intensity profile of the pulse in a plane orthogonal to the direction of the laser beam 3 varies and in particular can also _fall below the threshold F _thr .

Thus, the actual single-pulse ablation volume is given by the following formula:

The single-pulse ablation volume therefore depends non-linearly on the angle of inclination of the surface and the fluence profile F _P (x, y).

ergibt. c ist hierbei ein Proportionalitätsfaktor, der sich aus der Anordnung der Auftreffpunkte der Pulse des Laserstrahls ergibt. Beispielsweise gilt bei einem näherungsweise quadratischen Muster c = 1, während bei einem näherungsweise hexagonalen Muster c = 2/√3 gilt.In known single-pulse ablation volumes, it is possible with known simple generation methods, as described, for example, in US Pat DE 197 27 573 C1 or EP 1060710 A2 an ablation program are prepared according to which the mean ablation depth D _M varies uniformly or slowly varying at a distance d from the laser beam pulses directed onto the surface according to FIG

results. Here, c is a proportionality factor which results from the arrangement of the impact points of the pulses of the laser beam. For example, with an approximately quadratic pattern, c = 1, while with an approximately hexagonal pattern, c = 2 / √3.

In the following it is assumed that the ablation profile, as well as the water content, is spatially slow with respect to the length of the distance d or the slope is slowly opposite the diameter of the laser beam 3 changed on the surface. In order to describe the spatial dependence of these spatially slowly varying quantities, we will now use coordinates u and v which are given in a uv-coordinate system that coincides with the xy-coordinate system. The single-pulse ablation volume is therefore to be regarded as a function of u and v, as well as the average depth D _M resulting from the juxtaposed pulses.

The effective depth of ablation then results

In formula (9) now only D _{P, W} needs to be replaced by D _{M, Ist} , where V is _{pulse, is} under use of formula (14) in which D _{P is} replaced by D _{P, W} is determined.

In order to determine the locations to which laser pulses are to be applied, various known methods can be used, for example those already mentioned above DE 19727573 C1 and EP 1060710 A2 described method. In DE 19727573 C1 the ablation is carried out in layers, that is, impact or target locations for pulses are determined in layers, with the desired profile then being obtained by superposition of these layers. In the method in EP 1060710 A2 The spot distance is varied quasi-continuously to achieve the desired ablation depth.

The calculation of the modification function is explained using the example of the ablation of a spherical surface with a laser beam with a Gaussian beam profile (cf. 3 ).

beschrieben, wobei F₀ der Spitzenwert der Fluence, r der radiale Abstand zum Zentrum des Strahlprofils und w der Abstand ist, nach dem das Profil relativ zu dem Wert im Zentrum auf 1/e abgefallen ist.The beam profile or fluence is given by the formula

where F _{0 is} the peak of the fluence, r is the radial distance to the center of the beam profile and w is the distance after which the profile has dropped to 1 / e relative to the value in the center.

so daß sich das Einzelpuls-Ablationsvolumen für diesen Puls zu

berechnet. Als mittlere Tiefe des gewünschten Profils bei einem quadratischen Muster der Auftreffpunkte der Pulse bzw. Spot-Muster mit Kantenlänge a ist eine mittlere Tiefe der Ablation gemäß

zu erwarten. Setzte man nun D_E gleich D_Soll so könnte d als Funktion des Ortes ermittelt werden.This results in the actual ablation profile of a laser pulse which impinges orthogonally on a flat surface:

so that the single-pulse ablation volume for this pulse to

calculated. As the average depth of the desired profile in a square pattern of the impingement points of the pulses with spot length a, an average depth of the ablation is shown in FIG

expected. If you now set D _E equal to D _, then d could be determined as a function of the location.

In fact, however, except for the center, the spherical surface is incident to the laser beam, which is assumed to be incident to a sufficiently good approximation parallel to the z-axis 3 inclined. As it turned out 3 gives, the angle of inclination depending on the distance ρ of a place on the surface of the eye 2 calculated as follows:

The inclination of the surface at the location ρ now leads to the fact that both the spot distance in the direction of inclination and the spot width w in the direction of inclination are increased by the factor 1 / cos (θ (ρ)). Therefore, the ratio w / d in the equation for D does not change with the inclination. However, the fluence changes in this equation. Furthermore, μ now depends on the water content H, for example according to equations (6) and (7). The following result is obtained for the expected depth profile on the spherical surface:

systematic This result can also be obtained by the fact that in the Formula for the single-pulse ablation volume cos (θ) and μ = μ (H) as constant over the spot area is seen.

In 9 a laser ablation device is shown with a generating device or a control signal forming device according to another preferred embodiment of the invention, which differs from the laser ablation device of the first embodiment in that the data processing device 5 by a data processing device 5 ' is replaced and that a device 17 for recording the surface topography of the eye 2 is provided, which has a data connection with an interface 18 the data processing device 5 ' for reading surface topography data into the data processing device 5 ' connected is. Control commands for acquiring surface topography data to the device are also provided through this interface 17 dispensable. The other components are unchanged, so that the same reference numerals are used for these and the embodiments in the embodiment apply to these components here as well.

The device 17 For detecting the surface topography of the eye, the example may include an optical coherence tomograph.

The data processing device 5 ' differs from the data processing device 5 only through the interface 18 and the computer program with which the data processing device 5 ' or whose processor is programmed. The computer program comprises program code so that when the computer program is executed in the data processing device 5 ' the process described in the following is processed.

In order to determine the ablation program and to form and output the control signals, those shown in the flowchart in FIG 10 outlined method steps, of which the same reference numerals as in 5 designated steps are performed as in the first embodiment and the explanations to these steps apply here as well.

In Steps S10 and S12 or S14 and S16 thus become data the desired ablation profile or the water content of the corneal tissue determined and stored before ablation.

In the following step S18, a beam radius w and a preset fluence value F _{0 are} read in, which is the peak value of the fluence over the Gaussian beam profile of the laser 7 represents. The shape of the beam profile is taken into account by the formulas used.

Then, in the following step S30, it is driven by the data processing device 5 ' the surface topography of the area to be treated by means of the device 17 to detect the surface topography data. The corresponding data may include, for example, over a dot pattern in the xy plane detected heights of the surface relative to the xy plane.

In step S32, this data is then transmitted via the interface 18 for the surface topography data in the data processing device 5 ' read. From the elevation data, surface slopes are then determined by numerical determinations of gradients and the tilt angle formula given above. The corresponding data is then stored in the memory of the data processing device 5 ' saved.

The following steps then correspond to the steps of the method in the first embodiment, but now N _{W, i} is determined using formula (22) for D _{P, W} in equation (8).

On this way, there is a precompensation both in terms of Water content as well as the inclination of the surface and the shape of the beam profile such that their influences, when creating the ablation program with a simple Creation process neglected are taken into account, compensatory or precompensatory in advance and the actual ablation profile is very close to the target ablation profile comes.

The Ablation procedure is suitable for photorefractive keratectomy as well as LASIK. Because in this process material in different Layers of the eye will be removed, as appropriate different target ablation profiles are used.

The coherence tomograph of the institution 17 can be further used to determine the thickness of the cornea before and / or during ablation, ie to perform a pachymetric measurement. This can be avoided in particular that during ablation, the remaining thickness of the cornea falls below a predetermined minimum value.

In another embodiment, instead of the device 9 for performing confocal Raman spectroscopy, a temperature measuring device, for example with an infrared camera, whose optical axis is at an acute angle to the direction of the laser beam 3 is inclined to be used. This records data from which the temperature of the cornea and from this the water content of which can be determined spatially resolved.

Alternatively, instead of the facility 9 For performing confocal Raman spectroscopy, an optical coherence tomograph can be used, by means of which data, from which the refractive index of the cornea tissue can be calculated, can be detected. From the refractive index data can then by means of the data processing device 5 again the water content can be determined. The coherence tomograph may be present in addition to a coherence tomograph for determining the surface topography, if provided. However, it is also possible to use the same coherence tomograph for both functions. The coherence tomograph can be further used to determine the thickness of the cornea before and / or during ablation, ie to perform a pachymetric measurement. This can be avoided in particular that during ablation, the remaining thickness of the cornea falls below a predetermined minimum value.

Furthermore, a device for determining the air humidity in the area of the cornea can be provided which sends moisture data to the data processing device via a data connection 5 transfers where it can flow into the ablation depth model.

at further embodiments can depend on from the water content also the repetition rate, with the pulses on the material, or the cornea are delivered, modified.

Claims (36)

Method of creating an ablation program for the ablation of hydrous material from a surface ( 2 ' ) of a body ( 2 ) according to a predetermined target ablation profile by the delivery of pulses of a pulsed laser beam ( 3 ) on the surface ( 2 ' ), in which the ablation program is created from the target ablation profile taking into account a water content of the material to be ablated. Method according to Claim 1, in which, when the ablation program is drawn up, the water content is determined as a function of the location on the surface ( 2 ' ) or in an area to be ablated. Method according to claim 1 or 2, in which a model is used which determines the dependency of the at least one on a destination on the surface ( 2 ' ) delivered ablation depth or by at least one to a destination on the surface ( 2 ' ) delivered ablation volume of the water content of the material to be ablated with the pulse reproduces. Method according to one of the preceding claims, in which a further model is used which, for a given region of the material, determines the influence of pulses of the pulsed laser beam (14) which have impacted on this region or adjacent regions ( 3 ) on the water content. Method according to one of the preceding claims, in the data which reflect the water content or from which the water content can be determined. Method according to one of the preceding claims, in for consideration the water content during the creation of the ablation program Model for the water content or the change the water content of the material as a function of at least the Number and / or location previously on the same place and / or adjacent Places emitted pulses is used. Method according to one of the preceding claims, in which the water content in the body ( 2 ) measured data is determined. Method according to Claim 7, in which data which determine the temperature of the surface ( 2 ' ) play. Method according to claim 7 or 8, in which data are used to determine the water content, which reflect properties of optical radiation which are emitted by the material in the region of the body to be ablated ( 2 ). Method according to one of Claims 7 to 9, in which data obtained by confocal Raman spectroscopy of optical radiation from the surface ( 2 ' ) are available. Method according to one of claims 7 to 10, in which data are used to determine the water content, which reflect properties of fluorescence radiation emitted by the area of the body to be ablated ( 2 ). Method according to one of claims 7 to 11, wherein for the determination the water content data to be used, the refractive index in the material. Method according to one of the preceding claims, in for consideration of the water content from the predetermined target ablation profile dependent on determined by the water content pre-compensated ablation profile and from the precompensated ablation profile the ablation program is created. The method of claim 13, wherein for the determination the precompensated ablation profile has a modification function that is used explicitly or implicitly by the water content depends on the material to be ablated. The method of claim 14, wherein the value of Modification function at a given location of one Dependent on the location given by the target Ablationsprofil given Ablationstiefe. Method according to one of the preceding claims, in from the desired ablation profile a preliminary one Ablation program is created and used to form the Ablation program depending on at least one of the water content by the preliminary ablation program implicitly or explicitly specified fluence value or a by the provisional Ablation program implicitly or explicitly given pulse energy one on the one by the provisional one Ablation program given destination to be delivered pulse in dependence changed from the water content at the destination and as an indication of the destination is assigned. Method according to one of the preceding claims, in which the ablation program also depends on a shape of a beam profile of the laser beam ( 3 ) and / or a slope of the surface ( 2 ' ) is created. Method according to one of the preceding claims, in which, in order to take into account the shape of the beam profile and / or the inclination of the surface ( 2 ' ) from the target ablation profile using a modification function that depends on the shape of the beam profile and / or the inclination of the surface ( 2 ' ), in terms of influences of the shape of the beam profile and / or the inclination of the surface ( 2 ' ) pre-compensated target ablation profile is determined, and that from the determined with respect to influences of the shape of the beam profile and / or the inclination of the surface ( 2 ' ) precompensated target ablation profile the ablation program is created. Method for forming control signals for controlling a laser ( 7 ) of a laser ablation device for emitting a pulsed laser beam ( 3 ) and / or a deflection device ( 8th ) of the laser ablation device for deflecting the laser beam ( 3 ) to remove water-containing material from a surface ( 2 ' ) of a body ( 2 ) according to a predetermined target ablation profile by pulsing a pulsed laser beam ( 3 ), in which an ablation program for the predetermined target ablation profile is produced with the production method according to one of claims 1 to 18 and control signals are sent to the laser (in accordance with the ablation program). 7 ) and / or the deflection device ( 8th ). Method according to Claim 19, in which control signals are formed by means of which a laser beam used for ablation ( 3 ) debilitating modulator ( 16 ) is controllable in its transmission. Method according to Claim 19 or 20, in which control signals for driving the laser ( 7 ) of the laser ablation device, by means of which the fluence or pulse energy from the laser ( 7 ) Pulse is controlled. Method according to one of Claims 19 to 21, in which control signals for controlling a beam-shaping optical device in the beam path of the laser beam ( 3 ), which adjust the beam cross section serves, formed and delivered to the beam-shaping optical device. A method according to any one of claims 19 to 22, wherein the preparation of a first part of the ablation program and delivery corresponding control signals at least one further, still abarbeitender Part of the ablation program is created and appropriate control signals be delivered. Method according to one of claims 19 to 23, in which, starting from the desired ablation profile, a preliminary ablation program is created and for the preparation of the at least one further part of the ablation program for at least one destination on the surface given by the preliminary ablation program ( 2 ' ) the water content is determined, and the preliminary ablation program is changed to form the Ablationsprogramms depending on the determined water content. Device for creating an ablation program for the ablation of water-containing material from a surface ( 2 ' ) of a body ( 2 ) according to a predetermined target ablation profile by the delivery of pulses across the surface ( 2 ' ), pulsed laser beam ( 3 ) on the surface ( 2 ' ), comprises a data processing device ( 5 ; 5 ' ), which is designed to carry out the method for creating an ablation program according to one of claims 1 to 20. Apparatus according to claim 25, which is an interface ( 11 ) for collecting data representing the water content of the material or from which the water content can be determined. Device according to Claim 25 or 26, which has a control interface for a measuring device ( 9 ) for measuring data on the body ( 2 ), which reflect the water content or from which the water content can be determined, has, via the control commands for acquiring measured data to the measuring device ( 9 ) are deliverable. Device according to one of claims 25 to 27, comprising means for detecting a temperature of the surface, for transmission from captured Temperature data to the data processing device via a Data connection connected to the data processing device is. Device according to one of claims 25 to 28, which is connected to the data processing device ( 5 ; 5 ' ) connected spectrometer ( 9 ) for the analysis of the area of the body to be ablated ( 2 ) has outgoing optical radiation. Device according to one of Claims 25 to 29, comprising means for performing confocal Raman spectroscopy, which are used to transmit detected spectroscopy data to the data processing device ( 5 ; 5 ' ) with the data processing device ( 5 ; 5 ' ) connected is. Device according to one of claims 25 to 30, associated with the Data processing device connected device for detection of fluorescent radiation which, upon irradiation of the ablatierenden surface of the body of material on the surface of the body is delivered. Device for generating control signals for a laser and / or a deflecting device of a laser ablation device for removing water-containing material from a surface ( 2 ' ) of a body ( 2 ) according to a predetermined target ablation profile by pulsing a pulsed laser beam ( 3 ), the device comprising a generating device according to any one of claims 25 to 31 for the preparation of an ablation program from the predetermined desired ablation profile and a control device ( 6 ; 6 ' ) for the delivery of control signals according to the created ablation program to the laser ( 7 ) and / or the deflection device ( 8th ) for deflecting the laser ( 7 ) emitted laser beam ( 3 ). Device according to Claim 32, in which the control device ( 6 ' ) for the formation and delivery of control signals for driving a laser beam ( 3 ) debilitating modulator ( 16 ) is formed according to a created ablation program. Apparatus according to claim 32 or 33, wherein the Control device for generating and outputting control signals for Control of a beam-shaping optical device in the beam path the laser beam, which serves to adjust the beam cross section, according to one created ablation program is formed. Computer program with program code for the creation method according to one of claims 1 to 18 if the program is run on a computer ( 5 ; 5 ' ) is performed. A computer program with program code stored on a computer-readable medium for carrying out the method of creation according to any one of claims 1 to 18, when the computer program product is stored on a computer ( 5 ; 5 ' ) is performed.